Effects of capillary discharge current on the time of lasing onset of soft x-ray laser at low pressure

Zhao, Yijun; Cheng, Yuanyuan; Luan, Bohan; Wu, Yinchu; Wang, Qi

doi:10.1088/0022-3727/39/2/015

Cited by 45 publications

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References 12 publications

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“…1b. The spike of Xe plasma emission is wider than the 46.9 nm laser spike (~2 ns) [11,12] in pulse duration. Therefore, the spike of Xe plasma emission should be carefully studied to make certain whether it is a laser spike or not.…”

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confidence: 85%

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Experimental Study of Soft X-ray Emission from Pd-Like Xe Pumped by Capillary Discharge

Zhao

Xie

et al. 2014

J Appl Spectrosc

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Under different pressures, the temporal evolution and spectra of soft X-ray emission from a capillary discharge xenon plasma were measured with an X-ray diode and spectrometer, respectively. Transition lines from Xe 8+ to Xe 11+ were clearly observed and showed up as small spikes in the temporal profi le. Within the 5-20 nm wavelength region, the spectra originating from transitions in the Xe 8+ to Xe 11+ ion species were observed bet ween 9 and 19 Pa. Among these spectral lines, the 16.47 nm line arises from the transition between the 4d 9 5p 1 P 1 level and the ground level of Pd-like xenon (Xe 8+ ). The 4d 9 5p 1 P 1 level is the lower level of the 41.8 nm laser transition of 4d 9 5d 1 S 0 -4d 9 5p 1 P 1 . However, lasing output at 41.8 nm was not observed. According to our analysis, in order to realize the 41.8 nm lasing output, it is necessary to increase the electron temperature and the abundance of Pd-like Xe ions in the capillary discharge plasma.Introduction. Soft X-ray lasers pumped by capillary discharge have been demonstrated to be a promising scheme that meets practical requirements in applications [1]. Ever since the fi rst demonstration of a discharge pumped table-top soft X-ray laser by J. J. Rocca in 1994, there have been realized Ne-like Ar 46.9 [2] and 69.8 nm [3], Ne-like S 60.8 nm [4], and Ne-like Cl 52.9 nm [5] soft X-ray lasers pumped by capillary discharge. The Ne-like Ar 46.9 nm soft X-ray laser was amplifi ed in a highly saturated regime, and its average laser output pulse energy of 0.88 mJ and peak power of 0.6 MW were obtained at a repetition rate of 4 Hz [6]. Ne-like ions have a stable closed shell confi guration, which is favorable to maintain the gain time of the laser.Despite the early success of Ne-like Ar 46.9 nm soft X-ray laser, no soft X-ray laser with wavelength shorter than 46.9 nm has been realized by capillary discharge based on the electron collisional excitation scheme. A shorter wavelength laser has many advantages such as diagnostics of higher density plasmas, higher resolution metrology, and so on. Therefore, it is of signifi cant importance to realize shorter wavelength lasers with the electron collisional excitation scheme in a capillary discharge plasma. Because of this, we are focusing on soft X-ray lasers at 41.8 nm in Pd-like Xe (Xe 8+ ), which have a stable closed shell confi guration. Based on the collisionally pumped optical-fi eld-ionization (OFI) scheme, many groups have obtained Pd-like Xe 41.8 nm amplifi cation pumped by a femtosecond laser system [7-10]. The saturated amplifi cation of Pd-like Xe 41.8 nm lasers has been realized with the OFI scheme [8]. Compared to the OFI scheme, the capillary discharge scheme has the advantage of longer plasma length, lower cost, and simpler operation. It is believed that a Pd-like Xe 41.8 nm soft X-ray laser can be achieved with higer energy, longer gain lifetime, better beam quality, longer gain length, and higher energy conversion effi ciency.In this paper, by discharging gaseous xenon in a capillary to Z-pinch th...

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confidence: 85%

“…Experiment Setup. This experiment was conducted with the apparatus described in [11], in which Ne-like Ar 46.9 nm [11] and 69.8 nm [3] laser output pumped by a capillary discharge has been reported. The capillary is 3 mm in inner diameter and 35 cm in length.…”

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confidence: 99%

Experimental Study of Soft X-ray Emission from Pd-Like Xe Pumped by Capillary Discharge

Zhao

Xie

et al. 2014

J Appl Spectrosc

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“…The capillary discharge setup used to conduct the experiments was described in the previous publications [23,24]. The main pulse generator consists of a 7 nF Blumlein line filled with de-ionized water.…”

Section: Methodsmentioning

confidence: 99%

Characteristics of a multi-wavelength Ne-like Ar laser excited by capillary discharge

et al. 2016

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other applications. In 1994, J. J. Rocca et al. reported the first demonstration of large soft X-ray amplification in the plasma of a capillary discharge [1]. A population inversion between 2p 5 3p 1 S 0 and 2p 5 3s 1 P 1 (J = 0-1) in the Ne-like Ar ions was produced by the electron collisional excitation, and the gain coefficient at 46.9 nm (A line) was measured as 0.6 cm −1 . A saturated Ne-like Ar soft X-ray laser at 46.9 nm pumped by capillary discharge has produced millijoule-level laser pulses at a repetition rate of 4 Hz [2] and has led to many applications such as the diagnostics of dense plasma [3], lithography [4], nanoimaging [5], nanomachining [6] and material ablation [7].Other groups also had developed 46.9 nm laser pumped by capillary discharge [8][9][10][11][12][13][14][15][16]. Some groups studied the 46.9 nm laser with a low current, which is benefit to reduce the size and enhance the repetitive frequency of the laser. G. Niimi et al. firstly reported the observation of 46.9 nm laser output at a low discharge current of 9 kA [8]. G. Tomassetti et al. reported that 46.9 nm laser was realized with low amplitude 17-20 kA current pulses at pulse repetition rate up to 0.1 Hz [9]. The saturated laser at 46.9 nm was achieved by C. A. Tan et al. using the main current as low as 16 kA [13]. However, the other Ne-like Ar lasers were not observed by these groups.Except for J = 0-1 transition at 46.9 nm, EUV lasers can also be expected on some other 3p-3s transitions of Ne-like Ar in principle. The populations and gain coefficients of the 3p-3s transitions in Ne-like Ar were investigated by D. E. Kim et al. in theory [17]. It was found that large gains on the 3p 1 S 0 -3s 1 P 1 (J = 0-1), 3p 3 P 2 -3s 1 P 1 (J = 2-1) and 3p 3 D 2 -3s 3 P 1 (J = 2-1) transitions were formed for the electron density between 10 18 and 10 19 cm −3 . Due to the observation of intense laser on 3p 1 S 0 -3s 1 P 1 (J = 0-1) transition at 46.9 nm (A line), the two other lasers on 3p 3 P 2 -3s 1 P 1 (J = 2-1) transition at 69.8 nm (C line) and 3pAbstract We report the characteristics of 46.9, 69.8 and 72.6 nm lasers of Ne-like Ar in a plasma column pumped by capillary discharge. A main current of 12 kA with rise time of 40 ns was used to generate the plasma in a 35-cmlong capillary. The temporal and spatial characteristics of 46.9 and 69.8 nm laser pulses were measured. The time of lasing onset for the two lasers is about 35 ns. The pulse widths are about 1.3 ns for 46.9 nm laser and 1.2 ns for 69.8 nm laser. The FWHM beam divergences of the 46.9 and 69.8 nm lasers are approximately 0.5 and 0.4 mrad, respectively. The initial pressure ranges for 46.9, 69.8 and 72.6 nm lasers correspond to 13-24, 12.5-20 and 14-20 Pa, respectively. A gain coefficient of 0.58 cm −1 was measured and gain saturation behavior was observed at 46.9 nm, conditioning the initial pressure of 19 Pa. At the same discharge current, a 69.8 nm laser with gain coefficient of 0.41 cm −1 and a 72.6 nm laser with gain coefficient of 0.22 cm −1 were achieved by changing...

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“…This soft X-ray lasing demands optimization of various parameters which include: discharge current amplitude, its rate of rise (dI/dt), initial gas pressure, pre-pulse conditions (pre-pulse amplitude and its timing with respect to the discharge current) and the capillary dimensions (length and inner diameter). Various studies had been made to understand the effect of some of these parameters like (1) gas pressure, (2) pre-pulse amplitude and its delay with respect to the main pulse and (3) current pulse duration on the output of capillary discharge X-ray laser [12,13,29,30]. Apart from these parameters, the capillary tube material has also an important role to play.…”

Section: Introductionmentioning

confidence: 99%

Effect of the rate of rise in discharge current on the output of a 46.9-nm soft X-ray laser based on capillary discharge

et al. 2016

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fast capillary discharge scheme, which has been demonstrated by several groups worldwide [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. This is based on collisional excitation pumping through a fast heating of the plasma. Such a soft X-ray laser has several applications in different areas of science and technology [16][17][18][19][20][21][22]. In fact, there exists a strong interest in extending the lasing wavelength toward shorter side. It is worth mentioning here that directed EUV emission has also been reported from discharge plasma at shorter wavelengths ranging from 12 to 16 nm [23]. Efforts are presently going on in this direction in various laboratories worldwide to demonstrate X-ray lasing at a wavelength of 13.4 nm in nitrogen z-pinch plasma using a capillary discharge system [24][25][26][27]. Unlike the 46.9-nm X-ray laser, this is based on recombination pumping scheme which requires fast heating of the plasma followed by fast cooling of the hot plasma. Whether it is collisional excitation pumping scheme or recombination pumping scheme, both require faster pumping of the plasma to achieve population inversion, which can be done using a fast current pulse having high rate of rise (dI/dt) to excite the plasma.The generation of X-ray laser through the fast capillary discharge scheme is based on passing a fast rising electrical current through a pre-ionized gas column in a ceramic capillary. The magnetic field generated by the discharge current exerts strong magnetic force acting radially inwards on the plasma column. As a result, the plasma column gets pinched to a highly ionized hot and dense column, which may have sufficient population of required ionization state for lasing under suitable conditions. With argon gas filled inside the capillary, Ar 8+ ions are the lasing species and collectively form the gain medium for X-ray laser at 46.9 nm. Collisional electron excitation of these ions creates population inversion between 3p 1 S 0 and 3s 1 P 1 energy levels, which leads to soft X-ray lasing at 46.9 nm Abstract The rate of rise in discharge current (dI/dt) is an important parameter in an X-ray laser pumped by fast capillary discharge. The effect of this parameter on the energy of an argon plasma-based 46.9-nm soft X-ray laser pulse has been experimentally studied. It was found that an X-ray laser pulse with ~2 μJ energy, which can be obtained at a discharge current of ~40 kA with dI/dt value of ~7.1 × 10 11 A/s, can also be obtained at a much lower peak current of ~26 kA if the quarter period (T/4) of the discharge current is made shorter to achieve a comparable dI/dt value. For a fixed T/4, the laser energy could be enhanced from 2 to 4 μJ for an increase in the dI/dt value from 7.1 × 10 11 to 1.3 × 10 12 A/s by increasing the peak current from 26 to 44 kA. It was also observed that for a fixed dI/dt, mere increase in the discharge current does not increase the laser energy.

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Effects of capillary discharge current on the time of lasing onset of soft x-ray laser at low pressure

Cited by 45 publications

References 12 publications

Experimental Study of Soft X-ray Emission from Pd-Like Xe Pumped by Capillary Discharge

Experimental Study of Soft X-ray Emission from Pd-Like Xe Pumped by Capillary Discharge

Characteristics of a multi-wavelength Ne-like Ar laser excited by capillary discharge

Effect of the rate of rise in discharge current on the output of a 46.9-nm soft X-ray laser based on capillary discharge

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